Efficacy of a low calcium diet compared to a low sodium diet in the prevention of kidney stones in patients with chronic nephrolithiasis

Introduction: Nephrolithiasis is a disease affecting the urinary tract that often presents as flank pain, nausea, vomiting, urinary frequency and urgency, and hematuria. Kidney stones are hard deposits most commonly consisting of calcium oxalate. Large kidney stones can obstruct the urinary tract, causing infection, diminished renal function, and even renal failure Patients who experience recurrent kidney stones may be burdened with multiple emergency room visits, surgical procedures, and ultimately experience an impaired quality of life. Dietary modifications are often recommended by health care professionals in order to decrease the formation of stones. While the reduction of dietary calcium remains the mainstay among healthcare professionals, a fairly new approach in the prevention of kidney stones includes the reduction of dietary sodium. This paper will address the efficacy of a low calcium diet compared to a low sodium diet on the prevention of nephrolithiasis. Methods: A literature search was completed through EBSCO Host, PubMed, and Science Direct. Seven articles were selected based on their relevance to the research question, study design, outcome measurements, and results. Results: Based on the literature review, a low sodium diet appears to be more efficacious in the prevention of kidney stones compared to a low calcium diet. One study showed that patients on a low calcium diet experienced twice the number of kidney stones as compared to patients on a low sodium diet. Another study revealed that a diet with normal calcium is more effective than a low calcium diet in reducing the risk of recurrent renal stones in men with chronic nephrolithiasis. Furthermore, results of a third study showed that a reduction in dietary sodium markedly improved idiopathic hypercalciuria by approximately 110 g/d more than a reduction in dietary calcium in patients with recurrent calcium stone disease. Discussion: According to the studies, a diet low in sodium is significantly effective in the prevention of kidney stones, while a diet low in calcium is not effective and may actually increase the risk of stone formation. The studies implemented inclusion criteria that ensured that participants were at a similar risk of kidney stone development and most of the studies required that participants have a history of at least one documented incidence of nephrolithiasis. The studies used measurements such as urinalysis, urine volume, and 24 hour urine collection test. Renal ultrasound, abdominal flat plate examination, and X-ray diffractometry were used to determine presence of kidney stones in some of the studies. Conclusion: A low sodium diet should be considered superior to a low calcium diet in the prevention of kidney stones. The six studies selected for review all support the efficacy of a low sodium diet and/or the inefficacy of a low calcium diet in the prevention of nephrolithiasis. The mechanism behind this is explained by the presence of oxalate. Normally, after calcium is ingested, a complex between calcium and oxalate forms in the intestines to be excreted in the stool. However if there is a decrease in calcium, more oxalate is readily available to be reabsorbed by the colon and ends up in the urinary tract, therefore causing formation of calcium oxalate stones. On the other hand, a low sodium diet will lead the kidney to increase calcium to increase calcium to maintain electroneutrality, thereby reducing the concentration of calcium in the urine